Chlorinated-Ti₃C₂T_F as a dual-functional buried interface on SnO₂ electron-transporting layers for 25.09% high-performance n-i-p perovskite solar cells

Fluorinated titanium carbide MXenes (Ti3C2TF) have been proven as interfacial materials for hole transport layers in perovskite solar cells (pero-SCs). The surface terminals of Ti3C2TF can be adjusted to regulate the work function (WF) of electron transport layers (ETLs). In this work, Ti3C2TF,OH,O was treated with HCl to obtain Cl-terminated Ti3C2TF (named Ti3C2TF,Cl). The resulting Ti3C2TF,Cl was employed as a buried interlayer between SnO2 and the perovskite, which provides the dual functions of reducing the WF of SnO2, leading to good ohmic contact between the ETL and the perovskite, and facilitating the growth of the perovskite and reducing lattice stress via alteration of the surface energy of the ETL and lattice matching with the perovskite. n-i-p pero-SCs based on FA(0.92)MA(0.08)PbI(3) achieved an excellent power conversion efficiency (PCE) of 25.09% with an open circuit voltage of 1.18 V. The optimized pero-SCs exhibit improved stability in N-2, light soaking conditions, and air with a relative humidity of 30-40%. Additionally, Ti3C2TF,Cl performs well in large-scale devices (1.1 cm(2)) with a PCE of 20.62%, and is adaptable to pero-SCs with different perovskite (FA0.85MA0.15PbI2.55Br0.45), which achieves an exceptional PCE of 24.05% and a high fill factor of 84.52%.